Electric taxi auto-guidance and control system

ABSTRACT

An auto-guidance and control method and system is provided for use in conjunction with an aircraft electric taxi system. Aircraft status data is obtained, and airport feature data accessed. A processor generates taxi path guidance and control information including at least taxi speed guidance information, and sends commands derived from the taxi speed guidance information by the processor directly to an electric taxi controller to regulate the taxi speed of the aircraft.

TECHNICAL FIELD

Embodiments of the subject matter described herein relate generally toavionics systems such as electric taxi systems. More particularly,embodiments of the subject matter relate to an automatic guidance andcontrol system for an aircraft electric taxi system.

BACKGROUND

Traditional aircraft taxi systems utilize the primary thrust engines(running at idle) and the braking system of the aircraft to regulate thespeed of the aircraft during taxi. Such use of the primary thrustengines, however, is inefficient and wastes fuel. For this reason,electric taxi systems (i.e., traction drive systems that employ electricmotors) have been developed for use with aircraft. Electric taxi systemsare more efficient than traditional engine-based taxi systems becausethey can be powered by an auxiliary power unit (APU) of the aircraftrather than the primary thrust engines.

In its simplest form, a crew member may manually steer the aircraftduring an electric taxi maneuver using a flight deck controller (e.g. atiller) while looking out a window. In this case, the crew memberutilizes their best judgment regarding execution of their taxi maneuver.An improvement over this process is provided by a visual guidance systemwherein a crew member enters airport parameters such as airportcongestion, the visual guidance system determines the best taxi path,subject to ATC clearance, and presents it on a cockpit display alongwith instructions as to the best way to navigate the aircraft along thesuggested taxi path; e.g. speed, steering, when to thrust engines offand turn electric drive motors on, etc. ATC clearance can include taxiroute, assigned take-off or landing runway, hold points etc and isconsidered in the calculated path.

While effective, the above described visual guidance system exhibitscertain inefficiencies. For example, variations in complying withdisplay guidance instructions, even in the neighborhood of a fewseconds, may decrease fuel savings; e.g. a pilot waits a short timebefore turning thrust engines off. The pilot may execute faster turnsthan necessary resulting in increased tire wear, or brake more oftenthan necessary causing unnecessary wear and tear on the braking system.In addition, some actions that would increase efficiency are too subtlefor the crew to recognize and manage; e.g. optimum acceleration of theaircraft during taxi.

Accordingly, it would be desirable to provide an electric taxi automaticguidance and control system, capable of guiding and controlling anaircraft during a taxi maneuver with minimal crew intervention thusincreasing efficiency and reducing the work load of the crew.

BRIEF SUMMARY

In accordance with the foregoing, there is provided an auto-guidance andcontrol method for use in conjunction with an aircraft electric taxisystem, comprising obtaining aircraft status data, accessing airportfeature data, generating with a processor a taxi path guidance andcontrol information including at least taxi speed guidance information,and sending commands derived from the taxi speed guidance information bythe processor directly to an electric taxi controller to regulate thetaxi speed of the aircraft.

There is also provided a guidance and control system for use on-board anaircraft equipped with an electric taxi mechanism. The system comprisesa first source of aircraft status data, a second source of airportfeature data, and an electric taxi controller. A processor is coupled tothe first and second sources and to the electric taxi controller and isconfigured to generate taxi path guidance and control informationincluding at least taxi speed guidance information, and send commandsderived from the taxi speed guidance information directly to theelectric taxi controller.

An auto-guidance and control method for use in conjunction with anaircraft electric taxi system is also provided. Electric taxi guidancemay be performed in a manual mode by a crew or in an auto-mode by anauto-guidance and control system. The method comprises obtainingaircraft status data, accessing airport feature data, and generating ina processor, in response to at least the aircraft status data and theairport feature data, taxi guidance information. The method alsocomprises rendering the taxi guidance information on a display, manuallynavigating a guidance route utilizing guidance information on thedisplay in the manual mode, and applying taxi-path commands generated bythe processor directly to taxi path guidance controllers in theauto-mode.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the subject matter may be derived byreferring to the following detailed description and claims whenconsidered in conjunction with the accompanying figures, wherein likereference numbers refer to similar elements throughout the figures.

FIG. 1 is a simplified schematic representation of an aircraft having anelectric taxi system;

FIG. 2 is a general block diagram of an exemplary embodiment of anautomatic electric taxi guidance system suitable for use on an aircraft;

FIG. 3 is a more detailed block diagram of a further exemplaryembodiment of an automatic electric taxi guidance system suitable foruse on an aircraft.

FIG. 4 illustrates a first user input device in the form of atouchscreen for use with the embodiment shown in FIG. 3;

FIG. 5 illustrates a second user input device in the form of atouchscreen for use with the embodiment shown in FIG. 3;

FIG. 6 is a detailed block diagram of a still further exemplaryembodiment of an automatic electric taxi guidance system suitable foruse on an aircraft;

FIG. 7 is a block diagram illustrating the data link sub-function of theembodiment shown in FIG. 3;

FIG. 8 is a block diagram illustrating the push back sub-function of theembodiment shown in FIG. 3; and

FIG. 9 is a flow chart illustrating an exemplary embodiment of anelectric taxi auto guidance method.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the subject matter or theapplication and uses of such embodiments. As used herein, the word“exemplary” means “serving as an example, instance, or illustration.”Any implementation described herein as exemplary is not necessarily tobe construed as preferred or advantageous over other implementations.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

Techniques and technologies may be described herein in terms offunctional and/or logical block components and with reference tosymbolic representations of operations, processing tasks, and functionsthat may be performed by various computing components or devices. Suchoperations, tasks, and functions are sometimes referred to as beingcomputer-executed, computerized, software-implemented, orcomputer-implemented. It should be appreciated that the various blockcomponents shown in the figures may be realized by any number ofhardware, software, and/or firmware components configured to perform thespecified functions. For example, an embodiment of a system or acomponent may employ various integrated circuit components, e.g., memoryelements, digital signal processing elements, logic elements, look-uptables, or the like, which may carry out a variety of functions underthe control of one or more microprocessors or other control devices.

The system and methods described herein can be deployed with any vehiclethat may be subjected to taxi operations, such as aircraft, ships, etc.The exemplary embodiment described herein assumes that an aircraftincludes an electric taxi system, which utilizes one or more electricmotors as a traction system to drive the wheels of the aircraft duringtaxi operations. The system and methods presented here provide guidanceinformation to the flight crew for purposes of optimizing or otherwiseenhancing the operation of the electric taxi system. Such optimizationmay be based on one or more factors such as, without limitation: fuelconservation; prolonging the useful life of the brake system; avoidingground vehicles or other aircraft; and reducing taxi time. In certainembodiments, the taxi guidance information is rendered with a dynamicsynthetic display of the airport field to provide visual guidance to theflight crew. The taxi guidance information may include a desired taxiroute or path, a target speed for the electric taxi system to maintain,a graphical indicator or message that identifies the best time to turnthe primary thrust engine(s) on or off, best time to turn on or shut offthe auxiliary power unit (APU) or the like. The display system may beimplemented as an onboard flight deck system, as a portable computer, asan electronic flight bag, or any combination thereof.

FIG. 1 is a simplified schematic representation of an aircraft 100. Forthe sake of clarity and brevity, FIG. 1 does not depict the vast numberof systems and subsystems that would appear onboard a practicalimplementation of the aircraft 100. Instead, FIG. 1 merely depicts someof the notable functional elements and components of the aircraft 100that support the various features, functions, and operations describedin more detail below. In this regard, the aircraft 100 may include,without limitation: a processor architecture 102; one or more primarythrust engines 104; an engine-based taxi system 106; a fuel supply 108;wheel assemblies 109; an auxiliary power unit (APU) 110; an electrictaxi system 112; and a brake system 114. These elements, components, andsystems may be coupled together as needed to support their cooperativefunctionality.

The processor architecture 102 may be implemented or realized with atleast one general purpose processor, a content addressable memory, adigital signal processor, an application specific integrated circuit, afield programmable gate array, any suitable programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination designed to perform the functions described herein. Aprocessor device may be realized as a microprocessor, a controller, amicrocontroller, or a state machine. Moreover, a processor device may beimplemented as a combination of computing devices, e.g., a combinationof a digital signal processor and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with adigital signal processor core, or any other such configuration. Asdescribed in more detail below, the processor architecture 102 isconfigured to support various electric taxi guidance processes,operations, and display functions.

In practice, the processor architecture 102 may be realized as anonboard component of the aircraft 100 (e.g., a flight deck controlsystem, a flight management system, or the like), or it may be realizedin a portable computing device that is carried onboard the aircraft 100.For example, the processor architecture 102 could be realized as thecentral processing unit (CPU) of a laptop computer, a tablet computer,or a handheld device. As another example, the processor architecture 102could be implemented as the CPU of an electronic flight bag carried by amember of the flight crew or mounted permanently in the aircraft.Electronic flight bags and their operation are explained indocumentation available from the United States Federal AviationAdministration (FAA), such as FAA document AC 120-76B.

The processor architecture 102 may include or cooperate with anappropriate amount of memory (not shown), which can be realized as RAMmemory, flash memory, EPROM memory, EEPROM memory, registers, a harddisk, a removable disk, a CD-ROM, or any other form of storage mediumknown in the art. In this regard, the memory can be coupled to theprocessor architecture 102 such that the processor architecture 102 canread information from, and write information to, the memory. In thealternative, the memory may be integral to the processor architecture102. In practice, a functional or logical module/component of the systemdescribed here might be realized using program code that is maintainedin the memory. Moreover, the memory can be used to store data utilizedto support the operation of the system, as will become apparent from thefollowing description.

The illustrated embodiment of the aircraft includes at least two primarythrust engines 104, which may be fed by the fuel supply 108. The engines104 serve as the primary sources of thrust during flight. The engines104 may also function to provide a relatively low amount of thrust(e.g., at idle) to support a conventional engine-based taxi system 106.When running at idle, the engines 104 typically provide a fixed amountof thrust to propel the aircraft 100 for taxi maneuvers. When theengines 104 are utilized for taxi operations, the speed of the aircraftis regulated by the brake system 114.

Exemplary embodiments of the aircraft 100 also include the electric taxisystem 112 (which may be in addition to or in lieu of the engine-basedtaxi system 106 which typically provides a pilot with manual control ofthe aircraft). In certain implementations, the electric taxi system 112includes at least one electric motor (not shown in FIG. 1) that servesas the traction system for the drive wheel assemblies 109 of theaircraft 100. The electric motor may be powered by the APU 110 onboardthe aircraft 100, which in turn is fed by the fuel supply 108. Asdescribed in more detail below, the electric taxi system 112 can becontrolled by a member of the flight crew to achieve a desired taxispeed. Unlike the traditional engine-based taxi system 106, the electrictaxi system 112 can be controlled to regulate the speed of the drivewheels without requiring constant or frequent actuation of the brakesystem 114. The aircraft 100 may employ any suitably configured electrictaxi system 112, which employs electric motors to power the wheels ofthe aircraft during taxi operations.

FIG. 2 is a schematic representation of an exemplary embodiment of anautomatic guidance (auto-guidance) and control system 200 suitable foruse in conjunction with the aircraft 100. Depending upon the particularembodiment, the taxi auto-guidance system 200 may be realized inconjunction with a ground management system 202, which in turn may beimplemented in a line replaceable unit (LRU) for the aircraft 100, in anonboard subsystem such as the flight deck display system, in anelectronic flight bag, in an integrated modular avionics (IMA) system,or the like. The illustrated embodiment of the taxi auto-guidance system200 generally includes, without limitation: an engine start/stopguidance module 206; an electric taxi speed guidance module 208; asymbology generation module 210; a display system 212; an auto controlfunction (ACF) 205; manual/auto switch control 207; electric/auto brakeswitch control 209; and manual/auto nose wheel adaptor 211. The taxiguidance system 200 may also include or cooperate with one or more ofthe following elements, systems, components, or modules: databases 230;a controller 232 for the electric taxi system motor; at least one userinput device 234; a display module 236; sensor data sources 238; a datalink subsystem 240; and a source of neighboring aircraft location andstatus data 242 including collision sensors. In practice, variousfunctional or logical modules of the taxi guidance system 200 may beimplemented with the processor architecture 102 (and associated memory)described above with reference to FIG. 1. The taxi guidance system 200may employ any appropriate communication architecture 244 or arrangementthat facilitates inter-function data communication, transmission ofcontrol and command signals, provision of operating power, transmissionof sensor signals, etc.

The taxi guidance system 200 is suitably configured such that the enginestart/stop guidance module 206 and/or the electric taxi speed guidancemodule 208 are responsive to or are otherwise influenced by a variety ofinputs, and together with symbology generation 210 and display system212 comprise a visual electric taxi guidance system 213 (delineated witha dashed line). For this particular embodiment, the influencing inputsare obtained from one or more of the sources and components listed above(i.e., the items depicted at the left side of FIG. 2). The outputs ofthe engine start/stop guidance module 206 and/or the electric taxi speedguidance module 208 are provided to the symbology generation module 210,which generates corresponding graphical representations suitable forrendering with a synthetic display of an airport field. The symbologygeneration module 210 cooperates with the display system 212 to presenttaxi guidance information to the user.

The databases 230 represent sources of data and information that may beused to generate taxi guidance information. For example the databases230 may store any of the following, without limitation: airport locationdata; airport feature data, which may include layout data, coordinatedata, data related to the location and orientation of gates, runways,taxiways, etc.; airport restriction or limitation data; aircraftconfiguration data; aircraft model information; engine cool downparameters, such as cool down time period; engine warm up parameters,such as warm up time period; electric taxi system specifications; andthe like. In certain embodiments, the databases 230 store airportfeature data that is associated with (or can be used to generate)synthetic graphical representations of a departure or destinationairport field. The databases 230 may be updated as needed to reflect thespecific aircraft, the current flight plan, the departing anddestination airports, and the like.

The controller 232 represents the control logic and hardware for theelectric taxi motor. In this regard, the controller 232 may, in fact,comprise multiple controllers and/or include one or more user interfaceelements that enable the pilot to activate, deactivate, and regulate theoperation of the electric taxi system as needed. The controller 232 mayalso be configured to provide information related to the status of theelectric taxi system, such as operating condition, wheel speed, motorspeed, and the like.

The user input device 234 may be realized as a user interface thatreceives input from a user (e.g., a pilot) and, in response to the userinput, supplies appropriate command signals to the taxi guidance system200. The user interface may be any one, or any combination, of variousknown user interface devices or technologies, including, but not limitedto: a cursor control device such as a mouse, a trackball, or joystick; akeyboard; buttons; switches; or knobs, or even voice and gesturecommands. Moreover, the user interface may cooperate with the displaysystem 212 to provide a touch screen interface. The user input device234 may be utilized to acquire various user-selected or user-entereddata, which in turn influences the electric taxi guidance informationgenerated by the taxi guidance system 200. For example, the user inputdevice 234 could obtain any of the following, without limitation: aselected gate or terminal at an airport; a selected runway; user-enteredtaxiway directions; user-entered airport traffic conditions;user-entered weather conditions; runway attributes; and user options orpreferences.

The display module 236 may include a software application and/orprocessing logic to generate dynamic synthetic displays of airportfields during taxi operations. The display module 236 may also beconfigured to generate dynamic synthetic displays of a cockpit viewduring flight. In practice, the display module 236 cooperates with thesymbology generation module 210 and the display system 212 to rendergraphical indicia of electric taxi guidance information, as described inmore detail below.

The sensor data sources 238 represents various sensor elements,detectors, diagnostic components, and their associated subsystemsonboard the aircraft. In this regard, the sensor data source 238functions as sources of aircraft status data for the host aircraft. Inpractice, the taxi guidance system 200 could consider any type or amountof aircraft status data including, without limitation, data indicativeof: tire pressure; nose wheel angle; brake temperature; brake systemstatus; outside temperature; ground temperature; engine thrust status;primary engine on/off status; aircraft ground speed; geographic positionof the aircraft; wheel speed; electric taxi motor speed; electric taximotor on/off status; or the like.

The data link subsystem 240 is utilized to provide air traffic controldata to the host aircraft, preferably in compliance with known standardsand specifications. Using the data link subsystem 240, the taxi guidancesystem 200 can receive air traffic control data from ground based airtraffic controller stations and equipment. In turn, the system 200 canutilize such air traffic control data as needed. For example, the taxiclearance, assigned takeoff runway and other airport navigationinstructions may be provided by an air traffic controller using the datalink subsystem 240.

In an exemplary embodiment, the host aircraft supports datacommunication with one or more remote systems. More specifically, thehost aircraft receives status data for neighboring aircraft using, forexample, an aircraft-to-aircraft data communication module (i.e., thesource of neighboring aircraft status data 242) or an on-board collisionavoidance sensor. For example, the source of neighboring aircraft statusdata 242 may be configured for compatibility with Automatic DependentSurveillance-Broadcast (ADS-B) technology, with active Mode Sinterrogation technology, and/or with similar technologies.

The engine start/stop guidance module 206 and the electric taxi speedguidance module 208 are suitably configured to respond in a dynamicmanner to provide real-time guidance for optimized operation of theelectric taxi system. In practice, the taxi guidance information (e.g.,taxi path guidance information, start/stop guidance information for theengines, and speed guidance information for the electric taxi system)might be generated in accordance with a fuel conservation specificationor guideline for the aircraft, in accordance with an operating lifelongevity specification or guideline for the brake system 114 (see FIG.1), and/or in accordance with other optimization factors or parameters.To this end, the system processes relevant input data and, in responsethereto, generates taxi path guidance information related to a desiredtaxi route to follow. The desired taxi route can then be presented tothe flight crew in an appropriate manner. It should be noted that asused herein, the word “route” means the various directions an aircrafttakes to reach a target location. The word “path” comprises the “route”and the variations in acceleration, velocity, and braking along theroute. Thus, route may be shown in a single map and path is the routeincluding speed, acceleration, and breaking commands along the route.

The engine start/stop guidance module 206 processes relevant input dataand, in response thereto, generates start/stop guidance information thatis associated with operation of the primary thrust engine(s) and/or isassociated with operation of the electric taxi system.

As explained in more detail below, the start/stop guidance informationmay be presented to the user in the form of displayed markers orindicators in a synthetic graphical representation of the airport field.The electric taxi speed guidance module 208 processes relevant inputdata and, in response thereto, generates speed guidance information forthe onboard electric taxi system. The speed guidance information may bepresented to the user as a dynamic alphanumeric field displayed in thesynthetic representation of the airport field.

The symbology generation module 210 can be suitably configured toreceive the outputs of the engine start/stop guidance module 206 and theelectric taxi speed guidance module 208, and process the receivedinformation in an appropriate manner for incorporation, blending, andintegration with the dynamic synthetic representation of the airportfield. Thus, the electric taxi guidance information can be merged intothe display to provide enhanced situational awareness and taxiinstructions to the pilot in real-time.

The display system 212 includes at least one display element thatcooperates with a suitably configured graphics system (not shown), whichmay include symbology generation module 210 as a component thereof. Thisallows the display system 212 to display, render, or otherwise conveyone or more graphical representations, synthetic displays, graphicalicons, visual symbology, or images associated with operation of the hostaircraft on the display element, as described in greater detail below.In practice, the display element receives image rendering displaycommands from the display system 212 and, in response to those commands,renders a dynamic synthetic representation of the airport field duringtaxi operations.

The display element may be realized as an electronic display configuredto graphically display flight information or other data associated withoperation of the host aircraft under control of the display system 212.The display system 212 is usually located within a cockpit of the hostaircraft. Alternatively (or additionally), the display system 212 couldbe realized in a portable computer, and electronic flight bag, or thelike.

Referring still to FIG. 2, the outputs of the engine start/stop guidancemodule 206 and the electric taxi speed guidance module 208 are appliedto inputs of auto control function (ACF) 205, which controls theprocesses, procedures, and sub-functions associated with electric taxiauto-guidance and control. As can be seen, outputs of ACF 205 providecontrol and command signals to manual/auto switch control 207,electric/auto brake switch control 209, and manual/auto hose wheeladapter 211, described in more detail hereinafter in connection withFIGS. 3-8. For now, it should be appreciated that ACF 205 is primarilyresponsible for auto-guidance and control while visual guidance function213 may be monitored and available as a backup should a failure in theoperation of the auto guidance and control function occur.

FIG. 3. Is a schematic representation of an exemplary embodiment of anauto guidance and control system 300 suitable for use with aircraft 200wherein like elements are denoted with like reference numerals. As canbe seen, ACF 205 includes a number of sub-functions; i.e. surfaceguidance and hazard avoidance sub-function 302; optimal auto guidancesub-function 304; dual-path auto guidance sub-function 306; data linksub-function 308; brake warning and control sub-function 310, andpushback control sub-function 312. Each of these may reside in one ormore processors as described above, e.g. processor 102.

Surface guidance and hazard avoidance sub-function 302 is capable ofautomatically providing surface guidance and smart hazard avoidance toaircraft 100, and is capable of alerting the flight crew should such ahazard arise. To do this, surface guidance and hazard avoidancesub-function considers surveillance information from traffic includingsurrounding aircraft and ground vehicles 317. This information may beprovided and/or include (1) transponders on traffic equipped withAutomatic Dependence Surveillance Broadcast (ADS-B), Traffic InformationService Broadcast (TIS-B), or other sources such as on-board sensors;(2) own aircraft information and on-board sensors (e.g. radar orultrasonic sensors on wing-tips); and (3) airport taxiway and runwaydatabases including the cleared taxi route and assigned runway. Theguidance function and overall safety on the airport surface will beimproved by receiving halt information such as (1) taxi route andassigned runway information for other aircraft received from the otheraircraft or from Air Traffic Control (ATC); (2) planned speed andacceleration of other aircraft equipped with electric taxi control andguidance systems and data linked from the other aircraft; and (3)external signal lights for indicating intended actions to travelingaircraft including flashing lights and/or lights of different colors.Hazard alerts may be provided if an aircraft is in a potential hazardoussituation. Such alerts may be formulated within the auto-guidance andcontrol system and/or in other aircraft systems. Such alerts may includeadvisory, cautionary, and/or audible and visual alerts relating to, (1)potential collisions with other aircrafts or ground vehicles; (2)crossing or entering a runway occupied by another aircraft or groundvehicle; (3) aircraft deviation from an assigned taxi route; and (4)receipt or acceptance by the aircraft of a taxi clearance that includestaxiways and runaways that are not appropriate for the aircraft, e.g.aircraft too heavy or too wide.

Alerts may be auditory, visual, directive or non-directive and theresponse may be manual or automated. For example, an alert to warn of animpending collision may cause the system to automatically generate ahold if the crew does not take appropriate action such as moving thetiller, applying the brake, or manually pressing the hold button (eachdescribed below), within an appropriate time.

Surface guidance and hazard avoidance sub-function may also utilizeposition information of other aircraft to change the taxi path whenother aircraft, vehicles, or objects block the natural or assignedroute. In some cases, permission from the tower may be required todeviate from the assigned path. If there are two entrances to a runway,and a first aircraft is already waiting at one, the auto-guidance andcontrol system of a second aircraft may detect that an assigned entranceis blocked and determined a new path to the other entrance. Visualelectric taxi guidance system (VGS) 213 will display the new path optionand produce an alert to the crew who can accept or reject the new path.It the new path is rejected and the second aircraft continues along theexisting path, the crew may cause a hold or take manual control at theappropriate time. As usual in such situation the crew would contact thetower for instructions. If several aircrafts are in line for access to arunway for takeoff, the auto-guidance and control system can monitor theposition of the aircraft in front and then start, stop, and adjust thespeed as necessary to proceed in line.

Optimal auto guidance sub-function 304 determines the optimum path underbased on minimizing APU fuel, brake wear, tire wear, and electric drivewear. It may also take into account the need for timeliness; e.g. propergate time arrival and takeoff time. The crew may be able to choose amongoptions such as (1) minimal cost; e/g/ fuel, tire wear, etc., (2)timeliness; e.g. gate and runway time, and (3) minimum time. Optimumauto-guidance sub-function may utilize aircraft-specific parametersstored in the aircraft databases to make optimal path determinations. Inaddition, the crew may enter additional information such as runwaycondition if not already stored in the VGS.

If desired, electric taxi operation may be commenced whilesimultaneously utilizing a thrust engine if permitted by the aircraft;e.g. APU assist to engine-start. This permits the crew to start thethrust engines without coming to a complete stop. After the thrustengine start and predetermined parameters (e.g. speed) are reached, boththe electric taxi auto-guidance and control system and the electric taxidrive disengage. In a similar fashion, proper timing is determined forshutting the thrust engines off after landing to allow for propercooling. Some operational situations may extend this phase to the use ofone thrust engine with the electric taxi engaged for a period of time.

The automatic electric taxi guidance and control path may differ fromthe manual path guidance generated by visual electric taxi guidancesystem 213; e.g. the path guidance generated by the VGS. That is, theVGS may determine and display the target speed, but the auto guidancewill determine optimum acceleration, which would be difficult toaccomplish under manual control. The display system 212 (FIG. 2) willgraphically show the optimum auto-guidance path (auto-path) whenauto-guidance is engaged. When auto-guidance is not engaged, displaysystem 212 will show the manual guidance path. For example, the autopath display may provide an indication of how well the aircraft isachieving the optimum acceleration.

Dual path auto guidance sub-function 306 coordinates the two paths, autoand manual. When auto engaged, the dual path function ensures that thedisplay information relevant to auto control is displayed and the propercommands issued to the rest of the system. If auto mode is not engaged,the dual path function ensures that the display reflects manual guidanceinstructions and that commands are not sent to other systems. Data linksub-function 308 enables the tower to command the aircraft to halt or toprovide the aircraft with an alternate plan. The pilot may except orreject the plan, typically after consultation with the tower.

Brake warning and control sub-function 310 can operate in two modes;i.e. a manual mode and an automatic mode. In the manual mode, aircraftmay be slowed or stopped by shutting off the electric drive motors andallowing the aircraft to coast to a reduced speed or stop. Additionally,the electric drive motors themselves may be used as an aid in braking ifregenerative braking is also employed to help reduce the aircraft speed.If additional braking is required, a warning is displayed on the VGSinstructing the crew to apply braking. In the automatic mode, the brakesare applied automatically.

In most cases, push-back from the gate is accomplished using tugs whileground personnel monitor the maneuver. However, the ACF may be equippedwith a pushback control sub-function 312 which may cooperate with otherequipment such as rear facing cameras and a proximity detection systemusing, for example, ultrasonic sensors 314. The electric guidance andcontrol system may determine the pushback path and generate a hold, ifnecessary. Pushback control sub-function 312 limits speed and controlbraking.

As stated previously, VGS 213 is coupled to AFC 205. Also coupled to VGSare the various aircraft sensors; e.g. tire pressure sensors, braketemperature sensors, pushback sensors, etc.; one or more control panels316 and user input devices 326 (discussed in more detail in conjunctionwith FIGS. 4 and 5), and a surveillance and surface safety alertfunction 318. The surveillance and surface alert function 318 performstraffic and other hazard avoidance not specific to whether there is anelectric taxi system onboard. This function receives trafficsurveillance data from traffic surveillance 317, and the alerts fromthis system may be fed to surface guidance and hazard avoidance function302. Surveillance and surface safety alert function 318 also receivesADS-B In data and collision avoidance data, both of which can also beprovided to surface guidance and hazard alert sub-function 302. Surfaceguidance and hazard alert sub-function 302 then determines theappropriate action, if any, for the electric taxi system: e.g. brake,slow down, etc.

The surveillance and surface safety alert function is represents anexisting system on the aircraft that performs traffic and other hazardavoidance that isn't specific to whether or not there is an electrictaxi system on board. The alerts from this system can be fed into thesurface guidance and hazard avoidance sub-function 302. The surveillanceand surface safety alert function 318 also receives ADS-B In data andcollision avoidance data from sensors, both of which can also be fedinto the surface guidance and hazard avoidance sub-function which thendetermines what to do (e.g., brake, slow down, wait to perform someaction, or do nothing).

A control panel 316 is shown in FIG. 3 and enables a crew member tointerface with VGS 316 and therefore the entire auto-guidance andcontrol system. Control panel 316 may be separate or may be integratedwith other control panels. It may also be coupled to a user input device326 such as a keyboard, cursor control, touch screen or other inputdevice.

Manual/auto switch controller 207 is coupled to the electric taxicontrollers 320 and selectively applies either the manual controls orthe automatic controls to the left and right taxi controllers to adjustspeed. Electric/auto brake switch controller 209 is coupled to the brakecontrollers 322 and selectively permits either the auto-guidance andcontrol system or the normal aircraft braking commands to control theaircraft brakes. Manual/auto nose wheel adapter 211 is coupled to manualtiller 324. In some aircraft, adapter 211 contains the servo-mechanismsthat control the hydraulics which, in turn, control the nose wheel. Inother aircraft, the hydraulics are replaced with electronics. In anyevent, the manual/auto nose wheel adapter causes the auto-guidance to bedisengaged when tiller 324 is moved.

FIGS. 4 and 5 illustrate, user input devices, 400 and 500 respectively,suitable for communicating with VGS 213. Referring to FIG. 4, control402 (Engage Electric Taxi) engages and disengages the electric taxidrive, and control 404 (Engage Auto Control) engages the auto-guidanceand control function rather than simply displaying a possible airportroute.

FIG. 4 is shown and described as, for example, touch-screen. A firstactivation of Hold control 416 halts the aircraft but does not removethe aircraft from automatic guidance mode. A second activation of Holdcontrol will allow the aircraft to resume travel under auto guidance. Acrew member may initiate a hold, for example (1), upon receiving a holdinstruction from the tower; (2) while awaiting a clearance such asclearance to cross a runway; or (3) upon seeing an obstacle such as acrossing truck. A halt may be generated and Hold 416 illuminated if anon-board sensor detects an obstacle. If data link 308 (FIG. 3) isenabled, a halt may be generated by a command from the tower. A crewmember may initiate a hold, or a hold may be generated, when EngagePushback Control 414 is actuated and an aircraft is leaving the gatewithout using a tug.

It is contemplated that two path determinations may be made; (1)provisional, and (2) active. After the crew enters initial path data andengages auto guidance and control, the path becomes active. However, thecrew may need to modify the path during taxi (e.g. a new gate isassigned). The crew enters this provisional data and engages byactivating the Activate Provisional Plan control 422. The new path issent to the auto guidance and control system.

When the system detects an imminent collision, the auto-guidance andcontrol system commands a halt, and control 418 (Auto Avoid Override) isilluminated. Activating control 418 overrides the halt.

At times, the electric guidance and control system will generate a newsuggested path and present it on display system 212 (FIG. 2). The crewmay accept the suggested plan (Activate Suggested Plan 424) or rejectthe suggested plan (Reject Suggested Plan 420). If accepted, thesuggested plan becomes active. If rejected, the suggested plan iserased.

If Data link is enabled (control 406), the ATC clearance or other ATCinstructions can be input directly into the system. For example, a holdcommand could be sent or taxi clearance could be provided by the tower.If a new taxi clearance is sent, display system 212 displays a newsuggested path. This new suggested path may be accepted or rejected viacontrols 424 and 420, respectively as previously described.

If control 408 (Enable Auto Brake) is enabled, the electric autoguidance and control system will automatically apply brakes as needed.Otherwise, the crew will respond to warnings on the display. Control 410(Enable Auto Avoid) enables the auto guidance and control function toengage automatically upon landing. Enabling Auto Avoid (410) allows allthe obstacle avoidance functions such as the surface hazard or collisiondetection functions to generate a halt automatically. If this is notenabled then the crew depends solely upon their own observations to haltthe aircraft.

Region 428 is reserved for status and warning messages generated throughdata link 308 or by the auto-guidance and control system. A “Go to Menu”control 426 is also provided for this touch screen display to allow thecrew to display other system functions because the main touch panel isutilized for both auto-guidance and manual visual guidance (as well asother system functions; e.g. lighting, landing gear, etc.) Whenauto-guidance is selected, the touch panel appears as it does in FIG. 4.

For convenience, buttons may change from a first color to a second color(e.g. grey to green) when engaged or enabled by pushing and display alegend such as “Engaged” or “Enabled”. Hold 416 may be displayed in afirst color (e.g. blue) when activated by the crew and in a second color(e.g. green) when activated by the auto-guidance and control system.Auto Avoid Override 418 may blink (e.g. three times in blue) whenactivated. If a suggested or provisional plan is shown on display 212,controls 420 and 424 may be displayed in a first color (e.g. blue) andthen revert to a second color (e.g. grey) when a decision is made. Theengage/enable controls (402-414) may also be controlled by theirrespective related functions. For example, auto-brake (Enable Auto Brake408) will be displayed and revert to grey if there is a failure inbraking.

FIG. 5 illustrate a data entry screen 500, for entering taxi parameters,that may be separate or integrated with the control panel shown in FIG.4. A crew member may clear previously entered data (Clear All 502), andselect Takeoff (504) or Landing (506). The pilot may then enter airportdata (508), gate information (510) runway information (512), number ofaircraft waiting (514) and aircraft weight (516). When satisfied, thepilot may enter this data by activating Push to Transfer (518).

FIG. 6 is a block diagram illustrating the operation of the electrictaxi auto-guidance and control system in accordance with an embodimentfor a typical operation prior to landing and on the ground thereafter.Activating Engage Auto Control (404 in FIG. 4) causes AFC 205 to displaythe data entry page (FIG. 5) on VGS display system 212 (FIG. 2). Thecrew then enters the appropriate parameters and activates the transferbutton 518 (FIG. 5) causing the data to be transferred to the ACF 205wherein an auto-guidance path is determined and passed on to otherfunctions via dual path function 306. The path/route is also passed onto the VGS, and the auto guidance is displayed on the flight deck; e.g.display 212. This replaces the control panel information generated whenthe auto mode is disengaged. The paths are determined by dual pathfunction 306. That is, the system performs data entry for two pathcalculations: provisional and active. A crew member enters the initialpath data and engages. This path and targets are transferred to theauto-guidance and are “active”. However, during taxi the crew may needto modify the path (e.g. a new gate assigned). In this case, a crewmember pushes the provisional plan button to bring up the display shownin FIG. 5 and enters the required modifications. After returning to thecontrol panel display FIG. 4, the provisional button (now lighted) ispushed again to activate the provisional plan. The new path now replacesthe old and new target data is sent to the auto-guidance system. If notengaged within a predetermined period of time, (e.g. two minutes), theprovisional plan is ignored and erased, and the button is no longerilluminated. If the crew accepts the auto-guidance path, Engage ElectricTaxi 402 (FIG. 4) is activated, and AFC 205 transmits commandinformation to electric/auto brake switch control 209, manual/autoswitch control 207, and manual/auto nose wheel adapter 211 placing theaircraft in the auto-mode. AFC provides commands such as directioncommands, which are then utilized to control a nose wheel steeringmechanism 211 and manual tiller 64 is rendered inoperative. Whenelectric/auto brake switch control 209 is placed in the auto-mode, autobrake controllers 602 receive commands, speed, and status signals fromAFC 205 as to when to apply braking forces, rather than from manualbrake control 604. AFC 205 places manual/auto switch control 207 in theauto mode, and the right and left electric taxi controllers 610 and 612,respectively, receive commands from controllers 610 and 612 rather thanfrom manual controllers 606 and 608 on the flight deck; (e.g. joy sticksused to steer).

The landing process may be summarized as follows. Prior to landing, thecrew may enter airport parameters. This information may be received, inwhole or in part, via data link, if data link is enabled 406 (FIG. 4).If Enable Auto Landing 410 (FIG. 4) is activated prior to landing,Engage Auto Control occurs automatically after sensors detect a landing;(e.g. due to pressure on wheel switches), and the AFC has determinedwhen to turn the engines off and the action is performed by the crew.

If auto landing is not engaged, upon landing and after safe braking, thecrew engages auto control manually. It is assumed that at this point theAPU (110 in FIG. 1) is on. The aircraft begins maneuvering in accordancewith the taxi path shown on display 212 and generated by the autoguidance system. The crew monitors the displays and the path through thewindows to confirm proper operation and to disengage or hold, ifobstacles appear or there is a sudden change in circumstances; e.g. ablown tire. At a time determined by the electric taxi auto-guidance andcontrol system, the crew receives an indication of the optimum time toshut down the engines. The aircraft follows the auto-path and approachesthe gate area under auto control. The crew disengages auto-guidance forfinal gate approach and reverts to manual electric taxi control. Ifpermitted by the airport, the crew may use auto guidance to proceed tothe gate and park.

For takeoff, the crew first obtains taxi clearance and takeoffinformation. This may be obtained via voice or data link. Taxi clearanceis provided to the VGS via flight crew entry or automatically from thedata link. After turning on the APU 110 [FIG. 1], operation of theelectric taxi system is verified. The aircraft is typically pushed-backmanually and aligned to its initial position. The electric taxi autoguidance and control system is engaged and the aircraft beginsmaneuvering and taxi in accordance with the auto guidance system and theVFS. The crew monitors the displays and the terrain through the windowsto confirm proper operation and to disengage or hold if obstacles appearor there is a sudden change in circumstances. If auto-avoid is engagedthe system automatically detects hazards and may halt the system toprovide additional safety. At a time determined by the auto-guidancefunction, the crew is alerted as to the optimum time to start theengines. At the appropriate time, the crew disengages the electric taxiand guidance control system and the electric taxi system, and starts theengines.

If auto-pushback is available, Engage Pushback 414 (FIG. 4) may beactivated causing the aircraft to move back, turn, and align in therunway. It is to be noted that some aircraft configurations allow enginestart while the electric taxi auto-guidance and control system isengaged. In this case, the crew received an indication of the optimumtime to start engines. The auto guidance and electric taxi system maydisengage automatically after engine start.

FIG. 7 is a block diagram illustrating the operation of the data linksub-function 308 in ACF 205 when the tower commands a halt and thenprovides a new clearance. FIG. 7 shows a subset of the controls oncontrol panel 400 shown in FIG. 4; i.e. Engage Data-Link 406, Hold 416,Reject Suggest Plan 420, Activate Suggested Plan 424, and AdvisoryWindow 428 (in this case indicating that a new plan has been sent).Display 212 is also shown receiving data that originates in AFC 205which contains data link sub-function 308. Also shown is aircraftdata-link 700 for receiving information from an airport tower indictedby arrow 702. When the crew activates Engage Data Link 406, tower 702can command a forced halt or provide a suggested plan. Data Link 308provides the proper protocol and security to accept the halt command orcrew response to accept/reject (424/420) the new suggested route. If ahalt command is received, ACF 205 transmits the appropriate signals tothe braking, steering, and electric controls. Furthermore, AFC 205 sendsa warning to control panel 400 and to display 212. The suggested pathsent via the data link is displayed on display 212 where the crew mayaccept it (Activate Suggested Plan 424) or reject it (Reject SuggestedPlan 420).

FIG. 8 is a block diagram illustrating the operation of the pushbackcontrol sub-function 212 in AFC 205. Once again, a subset of the controlpanel 400 (FIG. 4) is shown in FIG. 8; i.e. Engage Auto Pushback 414,Hold 416, and Warning 410. In addition, data from Surface Guidance andAvoidance sub-function is available to Pushback Control sub-function312. When the Engage Auto Pushback control 414 is activated, a signal issent to AFC. The optimum path has already been calculated, and usingthis, the pushback control functions determine the additional commandsneeded to back the aircraft and turn the aircraft in the properdirection. After backup begins, the Surface Guidance and HazardAvoidance signals are transmitted, if needed, to the brake controllers602, electric taxi controllers 610 and 612, and nose wheel steeringmechanism 618 if Auto Avoid is engaged. The aircraft moves back alongthe determined backup path, turns in the proper direction in accordancewith the optimum path, and then halts. Hold light 416 turns on, theengage auto pushback light turns off, and warning panel 428 displays“Backup Complete”. If satisfied, the crew activates the halt control416, and auto-guidance along the guidance path continues.

If a collision is imminent, the aircraft halts, a warning is displayedidentifying the hazard that caused the halt, and the backupdiscontinues. If the cause of the halt is removed, pushback is restoredor the auto-guidance is disengaged, proceeding only with manual electriccontrol.

The electric taxi auto-guidance control system provides for a number ofinterlocks. For example, a data link command from traffic control maycause a halt as will brake activation by a crew member when auto brakeis activated. Furthermore, auto-control will disengage upon movement ofthe nose wheel steering tiller, excessive nose wheel angle, excessivelylow tire pressure, engine start, and excessive speed, parking brake set,change in flight configuration and the like. It is also contemplatedthat aircraft intent information be provided to neighboring aircraft andground vehicles so as to enable to take maneuvers originated by theelectric taxi auto-guidance and control system into account. This may beaccomplished using surface collision avoidance systems, ADS-B, externalsignal lights, and the like.

FIG. 9 is a flow chart that illustrates an exemplary embodiment of anelectric taxi auto-guidance process 900. The process 900 may beperformed by an appropriate system or component of the host aircraft,such as the taxi guidance system 200 shown in FIG. 2. The various tasksperformed in connection with process 900 may be performed by software,hardware, firmware, or any combination thereof. For illustrativepurposes, the following description of the process 900 may refer toelements mentioned above in connection with FIG. 1-8. In practice,portions of the process 900 may be performed by different elements ofthe described system, e.g., the processor architecture 102, the groundmanagement system 202, the symbology generation module 210, or thedisplay system 212. It should be appreciated that the process 900 mayinclude any number of additional or alternative tasks, the tasks shownin FIG. 9 need not be performed in the illustrated order, and theprocess 900 may be incorporated into a more comprehensive procedure orprocess having additional functionality not described in detail herein.Moreover, one or more of the tasks shown in FIG. 9 could be omitted froman embodiment of the process 900 as long as the intended overallfunctionality remains intact.

Although the auto-guidance process 900 could be performed or initiatedat any time while the host aircraft is operating, this example assumesthat the process 900 is performed after the aircraft has landed (orbefore takeoff). More specifically, the process 900 can be performedwhile the aircraft is in a taxi mode. The process 900 can be performedin a virtually continuous manner at a relatively high refresh rate. Forexample, iterations of the process 900 could be performed at a rate of12-40 Hz (or higher) such that the synthetic flight deck display will beupdated in real-time or substantially real time in a dynamic manner.

The auto-guidance process 900 obtains, receives, accesses, or acquirescertain data and information that influences the generation andpresentation of taxi guidance information. In this regard, the processmay acquire certain types of user-selected or user-entered data as inputdata (task 902). The user input data may include any of the informationspecified above with referent to the user input device 234 (FIG. 2). Forexample, the process 900 may contemplate user-selected oruser-identified gates, runways, traffic conditions, or the like. Theprocess 900 may also obtain or receive other input data (task 904) thatmight influence the generation and presentation of taxi guidanceinformation. Referring again to FIG. 2, the various elements, systems,and components that feed the taxi guidance system 200 may provide theother input data for task 904. In certain embodiments, this input dataincludes aircraft status data for the host aircraft (such as geographicposition data, heading data, and the like) obtained from onboard sensorsand detectors. The input data may also include data received from airtraffic control via the data link subsystems 240 and 308 (FIG. 3). Insome scenarios, the input data also includes neighboring aircraft statusdata for at least one neighboring aircraft in the airport field, whichallows the taxi guidance system 200 to react to airport traffic thatmight impact the taxi operations of the host aircraft.

The auto-guidance process 900 accesses or retrieves airport feature datathat is associated or otherwise indicative of synthetic graphicalrepresentations of the particular airport field (task 906). As explainedabove, the airport feature data might be maintained onboard theaircraft, and the airport feature data corresponds to, represents, or isindicative of certain visible and displayable features of the airportfield of interest. The specific airport features data that will be usedto render a given synthetic display will depend upon various factors,including the current geographic position and heading data of theaircraft.

The taxi auto-guidance system can process the user-entered input data,the other input data, and the airport feature data in an appropriatemanner to generate taxi path guidance information (task 908) for thehost aircraft, indicating start/stop guidance information for theprimary thrust engine(s) and/or for the electric taxi system, and/orspeed guidance information for the onboard electric taxi system, at theappropriate time and as needed. The resulting taxi path guidanceinformation, start/stop guidance information, and speed guidanceinformation will therefore be dynamically generated in response to thecurrent input data, real-time operating conditions, the current aircraftposition and status, and the like. Moreover, some or all of thegenerated guidance information may be influenced by the user-selected oruser-entered data, by the neighboring aircraft data, or by the airtraffic control data.

Although the electric taxi auto-guidance information could be conveyed,presented, or annunciated to the flight crew or pilot in different ways,the exemplary embodiment described here displays graphicalrepresentations of the taxi path guidance information, the enginestart/stop guidance information, and the speed guidance information.Surface traffic, if available, can also be displayed along with theaircraft route at the airport. More specifically, the process 900renders the electric taxi guidance information on a cockpit display.Accordingly, the process 900 may utilize the electric taxi guidanceinformation to generate image rendering display commands that are thenused to control the rendering and display of the airport field on thecockpit display (task 910). For this example, task 910 renders thedisplay of the airport field in accordance with the current geographicposition data of the host aircraft, the current heading data of the hostaircraft, and the airport feature data. As the graphical representationof the airport field might include graphical features corresponding totaxiways, runways, taxiway/runway signage, the desired taxi path, andthe like. A synthetic display may also include graphical representationsof an engine on/off indicator and a target electric taxi speedindicator. In practice, a dynamic synthetic display may also include asynthetic perspective view of terrain near or on the airport field. Incertain embodiments, the image rendering display commands may also beused to control the rendering of additional graphical features, such asflight instrumentation symbology, flight data symbology, or the like.

If the auto guidance option has not been selected (task 912), i.e.Engage Auto Control 404 (FIG. 4) has not been activated, the crewmanually operates the aircraft and follows a best taxi route on acockpit display with instructions as to how to best navigate thesuggested taxi path (task 914). That is, the visual taxi system willmake suggestions regarding speed, steering, when to turn thrust enginesand electric drive taxi motors on and off, etc. If, however, autoguidance has been enabled, AFC 205 will generate a new auto-taxi path(task 916) which will replace the best manual taxi path on the cockpitdisplay (task 918) with the auto-path generated by the AFC 205. Asdescribed earlier, the process continues with AFC 205 enabling the rightand left electric taxi controllers 610 and 612 (task 920), brakecontrollers 602 (task 922) and the nose wheel auto-steering mechanism618 (task 924).

If it is time to refresh the display (query task 926), then the process900 leads back to task 902 to obtain updated input data. If not, thenthe current state of the display is maintained. The relatively highrefresh rate of the process 900 results in a relatively seamless andimmediate updating of the display. Thus, the process 900 is iterativelyrepeated to update the graphical representation of the airport field andits features, possibly along with other graphical elements of thesynthetic display. Notably, the electric taxi guidance information mayalso be updated in an ongoing manner to reflect changes to the operatingconditions, traffic conditions, air traffic control instructions, andthe like. In practice, the process 900 can be repeated indefinitely andat any practical rate to support continuous and dynamic updating andrefreshing of the display in real-time or virtually real-time. Frequentupdating of the displays enables the flight crew to obtain and respondto the current operating situation in virtually real-time.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. For example, the techniques andmethodologies presented here could also be deployed as part of a fullyautomated guidance system to allow the flight crew to monitor andvisualize the execution of automated maneuvers. It should also beappreciated that the exemplary embodiment or embodiments describedherein are not intended to limit the scope, applicability, orconfiguration of the claimed subject matter in any way. Rather, theforegoing detailed description will provide those skilled in the artwith a convenient road map for implementing the described embodiment orembodiments. It should be understood that various changes can be made inthe function and arrangement of elements without departing from thescope defined by the claims, which includes known equivalents andforeseeable equivalents at the time of filing this patent application.

What is claimed is:
 1. An auto-guidance and control method for useon-board an aircraft in conjunction with an aircraft electric taxi drivesystem, comprising: obtaining aircraft status data; accessing airportfeature data; generating, with a processor, taxi path guidance andcontrol information including at least taxi speed guidance informationand taxi direction information; sending commands derived from the taxispeed guidance information by the processor directly to at least oneelectric taxi controller to regulate the taxi speed of the aircraft; andapplying steering commands derived from the taxi direction informationby the processor directly to a nose wheel steering mechanism to steerthe aircraft.
 2. An auto-guidance and control method according to claim1 wherein the taxi path guidance and control information includes atleast braking information and further comprising applying brakingcommands derived from the braking information by the processor directlyto electric taxi brake controllers.
 3. An auto-guidance and controlmethod according to claim 2 wherein the taxi path guidance and controlinformation is cost optimized by the processor in regards to taxi cost.4. An auto-guidance and control method according to claim 2 wherein theaircraft comprises a manual taxi steering mechanism and furthercomprising terminating auto-guidance upon activation of the manualsteering mechanism.
 5. An auto-guidance and control method according toclaim 2 further comprising halting the aircraft while remaining engagedin auto-guidance.
 6. An auto-guidance and control method according toclaim 2 further comprising generating commands by the processor forperforming auto-pushback of the aircraft from a gate.
 7. Anauto-guidance and control method according to claim 2 further comprisingmodifying the taxi path during taxi.
 8. An auto-guidance and controlmethod according to claim 2 further comprising receiving hazard data. 9.An auto-guidance and control method according to claim 8 furthercomprising generating commands to halt the aircraft when the processordetects a possible hazard.
 10. An auto-guidance and control methodaccording to claim 2 further comprising receiving ATC clearance via datalink.
 11. An auto-guidance method and control according to claim 2further comprising generating a halt command upon receipt of aninstruction from ATC.
 12. An auto-guidance and control method accordingto claim 2 further comprising receiving a new path from ATC.
 13. Anauto-guidance and control method according to claim 2 further comprisingdisplaying the path on a cockpit display.
 14. A guidance and controlsystem for use on-board an aircraft equipped with an electric taximechanism, the system comprising: a first source of aircraft statusdata; a second source of airport feature data; a third source of taxidirection information; a nose wheel steering mechanism; an electric taxicontroller; and a processor coupled to the first, second, and thirdsources, to the electric taxi controller, and to the nose wheel steeringmechanism and configured to (1) generate taxi path guidance and controlinformation including at least taxi speed guidance information and taxidirection information, and (2) send commands derived from the taxi speedguidance information directly to the electric taxi controller and to thenose wheel steering mechanism.
 15. A guidance and control systemaccording to claim 14 further comprising an electric taxi brakecontroller coupled to the processor, wherein the taxi path guidanceinformation includes at least braking information, and wherein theprocessor is further configured to send commands to the brakingcontroller.
 16. A guidance and control system according to claim 15further comprising a manual taxi steering mechanism and wherein theprocessor is further configured to terminate auto-guidance uponactivation of the manual steering mechanism.
 17. A guidance and controlsystem according to claim 14 wherein the processor is further configuredto receive hazard data.
 18. A guidance and control system according toclaim 14 wherein the processor is further configured to halt theaircraft upon detection of possible collision by the processor.
 19. Aguidance and control system according to claim 14 wherein the processoris configured to modify the taxi path during taxi.